Potassium carbamoylcarbamate

Endpoint summary

Additional information

The available stability, biodegradation, bioaccumulation, and adsorption/desorption data for potassium allophonate, indicate a substance that is highly water soluble, has a low potential for bioaccumulation, preferentially partitions in aqueous environments and is rapidly degraded through both biotic and abiotic (hydrolysis) processes.

Cheng et al. (2005) investigated the stability of 3 mM potassium allophonate in 10, 50, or 100 mM sodium phosphate buffer at pH 8.0, in 100 mM sodium phosphate buffer at pH 7.3, and in 7.3 mM sodium phosphate buffer at acidic pH (achieved by addition of perchloric acid) in 14-hour hydrolysis assays. Allophonate readily underwent decarboxylation to exclusively form urea at neutral and acidic pHs and in moderate to high buffer concentrations. When potassium allophonate was treated with 0.5 N perchloric acid, a half-life of seconds to minutes was determined. In 10 mM phosphate buffer at pH 8.0, a half-life of ca. 50 hours was estimated. When tested with 100 mM buffer, the estimated half life decreased significantly to ca. 17 hours. When tested with 100 mM buffer at pH 8.0, the half life was determined to be 3 hours. These data show that hydrolysis of potassium allophonate to urea will proceed at environmentally-relevant pH and that the rate of transformation increases as the pH becomes more acidic.

Available screening data show that potassium allophonate is readily biodegradable. A closed bottle ready biodegradability test performed according to Organisation for Economic Co-operation and Development (OECD) Testing Guideline 301D and in accordance with Good Laboratory Practice (GLP) requirements showed the allophonate reached >60% biodegradation within the 28-day test. Percent degradation was calculated by expressing biochemical oxygen demand (BOD) as a percent of theoretical oxygen demand (ThOD), which was calculated to be 0.84 mg O2/mg. The percent degradation on days 7, 14, 21, and 28 was 9.5, 46.7, 78.8, and 72.1%, respectively. Since >60% biodegradation was achieved within the 28-day test (the ten day window did not apply due to the test substance being a mixture), potassium allophonate may be classified as readily biodegradable.

No experimental data on bioaccumulation are available for potassium allophonate; however, based on an experimentally-determined log Pow ≤ -1.08 (ABC Laboratories, Inc., 2012a) and a lack of any lipophilic moieties in the chemical structure, the entire structure of potassium allophonate is hydrophilic and thus it has a low potential to cross biological membranes. Therefore, potassium allophonate has a low potential for bioaccumulation.

Organic carbon adsorption/desorption data are not available for potassium allophonate to assess transport and distribution in the environment. However, based on its physicochemical and environmental fate and transport properties, potassium allophonate is expected to have a low potential for adsorption to organic carbon. In a study performed according to OECD Testing Guideline 108 and under GLP, potassium allophonate was found to have an octanol-water partition coefficient (log Pow) of < -1.08 (ABC Laboratories, Inc., 2012a), indicating that preferentially partitions in the aqueous phase. Supporting this, a water solubility of value of 429.89 g/L at 23 °C was reported in a test performed according to OECD Testing Guideline 105 and under GLP (Intertek ASG, 2010). These data indicate that potassium allophonate has the potential to be transported in the environment through surface runoff. However, potassium allophonate has been found to be readily biodegradable in a closed bottle study performed according to OECD Testing Guideline 301D and under GLP (ABC Laboratories, Inc., 2013) and a study by Cheng et al. (2005) found rapid hydrolysis (half life of 4 hours at pH 7.3) of allophonate to urea at environmentally-relevant pH. Therefore, while potassium allophonate preferentially partitions in aqueous solutions, it is rapidly broken down in water and, therefore, has limited potential for transport and distribution in the environment. This is further supported by the fact that potassium allophonate has a negligible vapour pressure and is utilized by soil microorganisms as a nutrient source of nitrogen.

References:

ABC Laboratories, Inc. 2012a. Potassium Allophonate: Determination of n-Octanol/Water Partition Coefficient by High Performance Liquid Chromatography (HPLC). Testing laboratory: ABC Laboratories, Inc. 7200 E. ABC Lane, Columbia, MO 65202. Owner Company: Kerr Fire Fighting Chemicals, Ashcroft Rd., Knowsley Industrial Park, Kirby, Liverpool L33 7TS, England. Company study no.: 68014. Report date: 2012-05-14.

ABC Laboratories, Inc. 2013. Potassium Allophonate: Determination of the Ready Biodegradability Using the Closed Bottle Test Method. Testing laboratory: ABC Laboratories, Inc., 7200 E. ABC Lane, Columbia, MO 65202. Owner company: Kerr Fire Fighting Chemicals, Ashcroft Rd., Knowsley Industrial Park, Kirby, Liverpool L33 7TS, England. Company study no.: 68015. Report date: 2013-01-09.

Cheng, G., Shapir, N., Sadowsky, M. J. and Wackett, L. P. 2005. Allophonate hydrolase, not urease, functions in bacterial cyanuric acid metabolism. Applied and Environmental Microbiology, 71(8): 4437 -45.

Intertek ASG. 2010c. Potassium Allophonate Water Solubility. Testing laboratory: Intertek ASG. Report no.: 1320994. Owner company: Kerr Firefighting Chemicals. Report date: 2010-10-05.